1. Field Of The Invention
The present invention relates to machine tool jigs and fixtures. More specifically, the present invention relates to a cutting die press backing plate fixture and jig means for locating mounting points on a cutting die tool compatible with the present fixture.
2. Background Of The Invention
Mass production of complex article shapes cut from paper sheet such as envelope blanks includes a die cutting step wherein an approximately 500 sheet stack of envelope grade paper is simultaneously sheared by the single stroke of a die cutter mounted on the platen of a die cutting press. This system requires a cutting die formed from steel bar stock such as 1/2".times.4" forged to the peripherial outline of the article or envelope blank. For product size and shape flexibility, such cutting dies are removably secured to a mounting plate and the mounting plate removably secured to the backup plate structure of the press.
As the die advances into the sheet stack, the severed core of product is wedged within the peripherial enclosure of the die cutter structure. For removal, a fluid powered ejector ram is positioned coaxially of the backup plate to stroke through an aperture at the backup and mounting plate center against the cut article core wedged within the die. Such ejection forces are nearly as great as the original shear force required for the die cut. Consequently, the die mounting plate must be of heavy steel plate structure to resist lenticular deformation due to article ejection forces. For the same reason, the cutting die must be strongly secured to the mounting plate in addition to being conveniently removable therefrom.
A large producer of such sheet articles may have many different sizes of such die mounting plates (measured by the plate diameter) to accommodate the full spectrum of die sizes and shapes corresponding to his product line. Moreover, such a manufacturer may have numerous, geographically dispersed, production facilities.
Each product cutting die represents a substantial capital investment of time and labor. Although cutting dies are duplicated when necessary, such duplication is minimized due to the cost. Accordingly, it is customary for a manufacturer to ship a die between production facilities to meet local needs rather than duplicate the die at each facility. Consequently, each facility must prepare a companion mounting plate for each such transient die when first received.
If the foregoing example is expanded by hundreds of articles in a manufacturer's product spectrum, the need for maximum interchangeability between cutting dies and mounting plates is manifest. A hinderance to such interchangeability in the past has been the strong but removable interface connection between the cutting die and mounting plate.
The prior art technique of such matching is to blind drill and tap the back edge of a cutting die for machine screws at empirically selected locations around the die periphery. The centerlines of such tapped holes are then accurately transferred to the backing plate for drilling. Of simultaneous consideration is the need for the die to be secured to the backing plate symmetrically about the press ram axis for equal distribution of cutting and ejection forces on the cutting and ejecting hydraulic cylinders.
After a mounting plate has been drilled to receive the minimum of 4 mounting machine screws for each of approximately six different cutting dies, all more or less symmetrically distributed about the plate axis, the mounting plate approaches saturation for one or both of two reasons. Either the plate surface becomes confused with many holes making it difficult to find the correct hole combination for a particular cutting die or, the plate is structurally weakened by the excess removal of material.
When there are hundreds of such dies of diverse sizes and shapes, monumental mounting plate inventory storage and retrieval problems are created in order to find the correct mounting plate that has been drilled to receive a particular cutting die. Furthermore, since a single mounting plate is drilled to accommodate six or more dies, production conflicts arise when production needs require simultaneous use of two or more dies adapted for mounting on the same mounting plate.
Consequently, an unfulfilled desire of the industry has been to conceive a mounting system whereby any cutting die of a product spectrum may be secured to any appropriately sized mounting plate. One prior art attempt at solving this dilemma has taken the form of predrilled mounting plates according to a preconceived pattern. Unfortunately, no drill pattern has been conceived that will accommodate the infinite variety of size and shape dies required by the market. Often, the number and/or location of predrilled mounting plate holes is not compatible with the mounting strength requirements of a particular die configuration.
Another prior art approach to the problem is to cut a plurality of four to eight continuous radial slots in a mounting plate. Although this approach provides a sufficient number of universally aligned mounting points, the quantity of material removed from the mounting plate by the long slots unacceptably compromises the structural strength of the plate.
It is, therefore, an object of the present invention to teach a universal method and apparatus for combining cutting dies and mounting plates.
Another object of the present invention is to teach a pre-cut die mounting aperture configuration in mounting plates that is universally compatible with any die and does not compromise the structural strength of the plate.
Another object of the present invention is to teach a method and apparatus for quickly and accurately locating appropriate machine screw mounting points on any cutting die having compatability with a universal mounting plate aperture pattern.
Another object of the present invention is to teach a method and apparatus for quickly and accurately locating appropriate machine screw mounting points on a complex cutting die configuration for symmetrical security of the die about a respective mounting plate and backing plate axis.